A highly crosslinked wear surface formed by the reaction of a composition comprising a polyol and an aminoplast has been developed which has excellent scratch and stain resistance. However, since the surface of the highly crosslinked wear layer has only a trace amount of reactive functional groups, it has been extremely difficult to discover a composition which will adhere to the wear layer and which can be used as a seam coating.
As known in the art, when two sections of resilient sheet flooring are laid with two edges abutting, a seam is formed. Unless the seam is coated with a sealing composition, dirt tends to accumulate in the seam, and due to the slight difference in surface height between the two sections of resilient flooring at the seam, traffic will tend to snag the higher surface. A seam coating eliminates the crevice at the abutment and smooths the transition between the two elevations at the abutment.
Numerous seam coating compositions are known. Further a cyanoacrylate adhesive with dibutyl phthalate plasticizer is disclosed in European patent application Ser. No. 239,890. The invention of the European Application is an opaque cyanoacrylate adhesive or coating composition which comprises a monomeric ester of 2-cyanoacrylic acid and 5 to 50% by weight, based on the monomeric ester, of a semi-compatible plasticizer. The European application compares the opaque adhesive of the European invention with a non-opaque coating of cyanoacrylate with a fully compatible dibutyl phthalate plasticizer.
Since typical seam coatings would not adhere to the polyol/aminoplast wear layer, the surface was analyzed by the present inventors to determine if there were any functional groups present which could be used to gain adhesion. Only trace amounts of N--H, C--O, C.dbd.O and C--Cl were detected. Attempts to attack or soften the wear layer surface with solvents was also evaluated. The solvents were covered with watch glasses to retard evaporation. Of the nine solvents tested, only methylene chloride, tetrahydrofuran and methyl ethyl ketone softened and/or shriveled the surface of the wear layer within a twenty minute time period. However, if any of the above solvents were allowed to evaporate to dryness without restrictions, they had no effect on the surface of the wear layer.
Typical acrylic, nitrocellulose and vinyl lacquers utilizing these most active solvents were evaluated. The wear layer acted as a release coating and the lacquers failed to gain adhesion.
Many resinous systems including cyanoacrylates, alkyds, lacquers, epoxies, polyurethanes, and crosslinkable lattices were evaluated. The surface of the wear layer was pretreated with such agents as acids, alkali and corona discharge without improving the bonding characteristics.
One objective of the present invention is to provide a method of seam coating the surface of a wear layer comprising the reaction product of an aminoplast and a polyol.
A further object is to provide a seam coating composition which will adhere to the aminoplast/polyol wear layer and have excellent stain and scratch resistance as well as an appearance similar to the surface of the aminoplast/polyol wear surface.
These and other advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follows.